Soil tillage is a heavy-duty work and consumes a lot of energy. At present, plowing and rotary tillage are two main ways of soil tillage. By cutting soil orderly, plowing has good tillage performance and meets the demands for deep tillage. However, in order to meet the agronomic requirements, the plowed soil needs to be more harrowed, so, the tilling process is complicated, inefficient, energy-consuming and costly. Rotary tillers have both functions of plowing and harrowing. Meanwhile, it can till stubble, weeds, and green manure crops. Additionally, the tilled land remains level, and furrow slices are fragmented enough after rotary tilling. Therefore, rotary tilling can meet the agronomic requirements and race against tillage time. However, rotary tillage needs more energy, and its performance coverage is relatively poorer compared to plow tillage. So, it can make many plants on the topsoil and let weeds sprout earlier. With the rapid development of agricultural technology, cultivation techniques are also used in rhizome crop cultivation. In order to improve the quality and yield of rhizome crops, the quality of the cultivated soil is required more critically. Namely, tillage should increase the depth of tillage and make the soil looser. In order to meet the requirements of thickening soil maturation layer, improving soil aeration, increasing the water capacity and making more straws returned to the field, it is one of the leading research directions to increase the tillage depth, reduce energy consumption and improve tilling quality.
Currently, natural rotary tillage must increase the diameter of knife roller to increase the tillage depth because the knife shaft is located above the soil surface.
However, the large diameter of the knife roller will make the whole structure bulky and heavy, and the power consumption will increase sharply. According to current rotary tiller design theory, the soil cutting process starts when rotary blades below the rotary blade cutter center horizontal line and finishes to the rotary blade to the vertical position. However, when H=R×(1−1/λ), (Where R is the revolution radius, H is tillage depth, and λ is rotational speed ratio of rotary tillage. The level trail of the instantaneous rotational center of cutter falls on the ground, and the speed direction of the sidelong edge of the rotary blade is vertical downward. Meanwhile, rotary tilling blades have the minimum dynamic cutting angle, and the resistance of cutting soil is small. The target tilling depth H is determined depending on the agronomic requirements, and cutter radius R is decided by R≥H×λ(λ−1). Usually, λ (the value of rotational speed ratio of rotary tillage) is between 4˜10. In order to improve the harrow breaking rate, lower gully bottom roughness, and ensure a reasonable dynamic gap angle, the value of λ should take a larger value. In this way, the value of R is relatively small, and consequently, the rotary cultivator has the advantages of compact structure, but the power consumption will increase sharply with the tilling depth increasing. Meanwhile, the cutting soil resistance force direction of the knife cylinder points to the front top, and its vertical component force points upward, which will not be helpful for rotary tilling blades piercing soil. Especially, the blade back will squeeze soil when travel speed increase and leading rotary tillers to bump which influences the stability of tilling depth. If the horizontal resistance force of the knife roller is bigger than tractor rolling resistance and other horizontal resistances, the tractor will be pushed to slip in the process of cutting soil, and parasitic power will be generated. It will lead tractor driving system to be destroyed, increase tractor power consumption and lower tractor effective life.
The submerged reverse rotary tillage is a rotary tillage model of the rotary cutter shaft sinking below the surface. Because the rotation direction of rotary blade is averse to the rotation direction of the driving wheel of the tractor, submerged reverse rotary tillers cut soil clods from the bottom of the furrow, and more soil clods are broken by tension. So, submerged reverse rotary tillage can reduce the cutting resistance force, cutting torque, and soil crushing energy consumption. In addition, since the cutter shaft is below the soil surface, the submerged reverse rotary tillage can be achieved deep tillage by using a short blade. But the submerged reverse rotary tillage makes so many soil clods be thrown to the front of rotary tiller blade rollers and leading hipping. The phenomenon of hipping will cause re-tillage, and make the working load and power consumption increase rapidly. The rotary tillers will not able work if the hipping is very serious. Furthermore, in order to make the cutter shaft sink below the surface, we must design special part to avoid gearbox and bearing seat interfering with the uncultivated land. This will make the rotary tillers more complicated and lower transmission efficiency.